Green’s Dictionary of Slang

1. (Aus./US) a shoe.

1908		N.Y. Eve. Journal 21 Aug. in Fleming Unforgettable Season (1981) 178: Devlin had his foot between the bag and Lobert’s ‘kangaroos.’.
1999		G. Seal Lingo 91: kangaroo(s) are shoe(s), usually just kanga(s).

2. a Jew.

1943		M. Harrison Reported Safe Arrival 10: Harry was a Jew. In his own phrase: a ‘tin-lid.’ Otherwise, a ‘four-by- two,’ a ‘Kangaroo,’ or a ‘five-to-two’.
1959		J. Gosling Ghost Squad 24: Thieves’ argot, spoken properly, is a foreign language which needs to be learned [...] Among the words and phrases derived from rhyming slang are: [...] Sarah Soo, Four-by-two or Kangar (Kangaroo) means a Jew.
1961		(con. c.1935) R. Poole London E1 (2012) 83: ‘Jew-lover, ain’cha? Like the yids an’ the kanga’s, don’cha?’ The Jews were known as Yiddishers, and in rhyming slang as kangaroos.
1964		R.S. Gold Jazz Lex. xxiii: British formations in which the meaningful word, whether slang or standard, is usually replaced by a nonsense rhyming one: e.g., Kangaroo: a Jew; don’t make a fuss: a bus; down the drains: brains; Colney Hatch: a match.
1976		(ref. to 1928) R. Barnes Coronation Cups and Jam Jars 96: Around 1928 when Sir Oswald Mosely’s party was in full swing [...] Jews were the ones to hate then. Most East Enders knew them as ‘four-by twos’ or ‘kangaroos’.

3. a prison warder [screw n.¹ (2c)].

c.1943		‘Bill O. Lading’ You Chirped a Chinful!! n.p.: Kangaroo: Sergeant of the guard.
1968		Partridge DU (3rd edn) 838/1: kangaroo a prison warder ‘since ca. 1925’.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1984		Partridge DSUE (8th edn) 636: since ca. 1920.
1990		Tupper & Wortley Aus. Prison Sl. Gloss. 🌐 Kangaroo. Prison officer. Rhyming slang for ‘screw’.
2000		J.J. Connolly Layer Cake 7: They always made the kangas earn their shillings.